Keep input when users refresh currency rates (#369)

Fixes #260

Description of the changes:
prevent UnitConverterViewModel to reset values when users click on update rates.
recompute UnitConverter's caches (m_ratioMap and m_categoryToUnits) once rates are updated (but check first if the user did/didn't change the category)

How changes were validated:
Manually tested with fake currency rates (HTTP responses modified on the fly via FiddlerCore)
Verified that it works no matter the selected field (From or To)
Verified that the currencies selected are kept after a refresh

src/CalcManager/UnitConverter.cpp

@@ -63,7 +63,8 @@ UnitConverter::UnitConverter(_In_ const shared_ptr<IConverterDataLoader>& dataLo
     unquoteConversions[L"{sc}"] = L';';
     unquoteConversions[L"{lb}"] = LEFTESCAPECHAR;
     unquoteConversions[L"{rb}"] = RIGHTESCAPECHAR;
-    Reset();
+    ClearValues();
+    ResetCategoriesAndRatios();
 }
 
 void UnitConverter::Initialize()
@@ -75,7 +76,7 @@ bool UnitConverter::CheckLoad()
 {
     if (m_categories.empty())
     {
-        Reset();
+        ResetCategoriesAndRatios();
     }
     return !m_categories.empty();
 }
@@ -152,7 +153,6 @@ void UnitConverter::SetCurrentUnitTypes(const Unit& fromType, const Unit& toType
     Calculate();
 
     UpdateCurrencySymbols();
-    UpdateViewModel();
 }
 
 /// <summary>
@@ -336,7 +336,8 @@ wstring UnitConverter::Serialize()
 /// <param name="serializedData">wstring holding the serialized data. If it does not have expected number of parameters, we will ignore it</param>
 void UnitConverter::DeSerialize(const wstring& serializedData)
 {
-    Reset();
+    ClearValues();
+    ResetCategoriesAndRatios();
 
     if (serializedData.empty())
     {
@@ -615,7 +616,7 @@ void UnitConverter::SendCommand(Command command)
         clearFront = false;
         clearBack = false;
         ClearValues();
-        Reset();
+        ResetCategoriesAndRatios();
         break;
 
     default:
@@ -634,8 +635,6 @@ void UnitConverter::SendCommand(Command command)
     }
 
     Calculate();
-
-    UpdateViewModel();
 }
 
 /// <summary>
@@ -824,19 +823,16 @@ vector<tuple<wstring, Unit>> UnitConverter::CalculateSuggested()
         returnVector.push_back(whimsicalReturnVector.at(0));
     }
 
-    //
-
     return returnVector;
 }
 
 /// <summary>
-/// Resets the converter to its initial state
+/// Resets categories and ratios
 /// </summary>
-void UnitConverter::Reset()
+void UnitConverter::ResetCategoriesAndRatios()
 {
     m_categories = m_dataLoader->LoadOrderedCategories();
 
-    ClearValues();
     m_switchedActive = false;
 
     if (m_categories.empty())
@@ -881,7 +877,6 @@ void UnitConverter::Reset()
     }
 
     InitializeSelectedUnits();
-    Calculate();
 }
 
 /// <summary>
@@ -972,11 +967,21 @@ bool UnitConverter::AnyUnitIsEmpty()
 /// </summary>
 void UnitConverter::Calculate()
 {
-    unordered_map<Unit, ConversionData, UnitHash> conversionTable = m_ratioMap[m_fromType];
-    double returnValue = stod(m_currentDisplay);
-    if (AnyUnitIsEmpty() || (conversionTable[m_toType].ratio == 1.0 && conversionTable[m_toType].offset == 0.0))
+    if (AnyUnitIsEmpty())
     {
         m_returnDisplay = m_currentDisplay;
+        m_returnHasDecimal = m_currentHasDecimal;
+        TrimString(m_returnDisplay);
+        UpdateViewModel();
+        return;
+    }
+
+    unordered_map<Unit, ConversionData, UnitHash> conversionTable = m_ratioMap[m_fromType];
+    double returnValue = stod(m_currentDisplay);
+    if (conversionTable[m_toType].ratio == 1.0 && conversionTable[m_toType].offset == 0.0)
+    {
+        m_returnDisplay = m_currentDisplay;
+        m_returnHasDecimal = m_currentHasDecimal;
         TrimString(m_returnDisplay);
     }
     else
@@ -1015,9 +1020,9 @@ void UnitConverter::Calculate()
             m_returnDisplay = returnString;
             TrimString(m_returnDisplay);
         }
-    }
-
         m_returnHasDecimal = (m_returnDisplay.find(L'.') != m_returnDisplay.npos);
+    }
+    UpdateViewModel();
 }
 
 /// <summary>

src/CalcManager/UnitConverter.h

@@ -1,4 +1,4 @@
-// Copyright (c) Microsoft Corporation. All rights reserved.
+// Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT License.
 
 #pragma once
@@ -195,6 +195,8 @@ namespace UnitConversionManager
         virtual void SetViewModelCallback(_In_ const std::shared_ptr<IUnitConverterVMCallback>& newCallback) = 0;
         virtual void SetViewModelCurrencyCallback(_In_ const std::shared_ptr<IViewModelCurrencyCallback>& newCallback) = 0;
         virtual concurrency::task<std::pair<bool, std::wstring>> RefreshCurrencyRatios() = 0;
+        virtual void Calculate() = 0;
+        virtual void ResetCategoriesAndRatios() = 0;
     };
 
     class UnitConverter : public IUnitConverter, public std::enable_shared_from_this<UnitConverter>
@@ -218,6 +220,8 @@ namespace UnitConversionManager
         void SetViewModelCallback(_In_ const std::shared_ptr<IUnitConverterVMCallback>& newCallback) override;
         void SetViewModelCurrencyCallback(_In_ const std::shared_ptr<IViewModelCurrencyCallback>& newCallback) override;
         concurrency::task<std::pair<bool, std::wstring>> RefreshCurrencyRatios() override;
+        void Calculate() override;
+        void ResetCategoriesAndRatios() override;
         // IUnitConverter
 
         static std::vector<std::wstring> StringToVector(const std::wstring& w, const wchar_t * delimiter, bool addRemainder = false);
@@ -228,9 +232,7 @@ namespace UnitConversionManager
         bool CheckLoad();
         double Convert(double value, ConversionData conversionData);
         std::vector<std::tuple<std::wstring, Unit>> CalculateSuggested();
-        void Reset();
         void ClearValues();
-        void Calculate();
         void TrimString(std::wstring& input);
         void InitializeSelectedUnits();
         std::wstring RoundSignificant(double num, int numSignificant);

src/CalcViewModel/UnitConverterViewModel.cpp

@@ -165,12 +165,16 @@ void UnitConverterViewModel::PopulateData()
 }
 
 void UnitConverterViewModel::OnCategoryChanged(Object^ parameter)
+{
+    m_model->SendCommand(UCM::Command::Clear);
+    ResetCategory();
+}
+
+void UnitConverterViewModel::ResetCategory()
 {
     UCM::Category currentCategory = CurrentCategory->GetModelCategory();
     IsCurrencyCurrentCategory = currentCategory.id == NavCategory::Serialize(ViewMode::Currency);
 
-    m_model->SendCommand(UCM::Command::Clear);
-
     m_isInputBlocked = false;
     SetSelectedUnits();
 
@@ -706,7 +710,9 @@ void UnitConverterViewModel::OnCurrencyDataLoadFinished(bool didLoad)
 {
     m_isCurrencyDataLoaded = true;
     CurrencyDataLoadFailed = !didLoad;
-    ResetView();
+    m_model->ResetCategoriesAndRatios();
+    m_model->Calculate();
+    ResetCategory();
 
     StringReference key = didLoad ? UnitConverterResourceKeys::CurrencyRatesUpdated : UnitConverterResourceKeys::CurrencyRatesUpdateFailed;
     String^ announcement = AppResourceProvider::GetInstance().GetResourceString(key);

src/CalcViewModel/UnitConverterViewModel.h

@@ -223,6 +223,7 @@ namespace CalculatorApp
             void UpdateValue2AutomationName();
             Platform::String^ Serialize();
             void Deserialize(Platform::String^ state);
+            void ResetCategoriesAndRatio();
 
             // Saving And Restoring User Preferences of Category and Associated-Units across Sessions.
             void SaveUserPreferences();
@@ -263,6 +264,7 @@ namespace CalculatorApp
             void RefreshSupplementaryResults();
             void UpdateInputBlocked(_In_ const std::wstring& currencyInput);
             bool UnitsAreValid();
+            void ResetCategory();
 
             void OnButtonPressed(Platform::Object^ parameter);
             Platform::String^ ConvertToLocalizedString(const std::wstring& stringToLocalize, bool allowPartialStrings);

src/CalculatorUnitTests/UnitConverterViewModelUnitTests.h

@@ -42,11 +42,14 @@ namespace CalculatorUnitTests
             void SendCommand(UCM::Command command) override;
             void SetViewModelCallback(const std::shared_ptr<UCM::IUnitConverterVMCallback>& newCallback) override;
             void SetViewModelCurrencyCallback(_In_ const std::shared_ptr<UCM::IViewModelCurrencyCallback>& /*newCallback*/) override {}
+            void Calculate() override {}
+            void ResetCategoriesAndRatios() override{}
             concurrency::task<std::pair<bool, std::wstring>> RefreshCurrencyRatios() override
             {
-                co_return std::make_pair(L"", L"");
+                co_return std::make_pair(true, L"");
             }
 
+
             UINT m_initCallCount;
             UINT m_getCategoriesCallCount;
             UINT m_setCurrentCategoryCallCount;